Diethylcarbamazine activates TRP channels including TRP-2 in filaria, Brugia malayi.

Diethylcarbamazine is an important classic drug used for prevention and treatment of lymphatic filariasis and loiasis, diseases caused by filarial nematodes. Despite many studies, its site of action has not been established. Until now, the consensus has been that diethylcarbamazine works by activating host immune systems, not by a direct action on the parasites. Here we show that low concentrations of diethylcarbamazine have direct and rapid (<30 s) temporary spastic paralyzing effects on the parasites that lasts around 4 h, which is produced by diethylcarbamazine opening TRP channels in muscle of Brugia malayi involving TRP-2 (TRPC-like channel subunits). GON-2 and CED-11, TRPM-like channel subunits, also contributed to diethylcarbamazine responses. Opening of these TRP channels produces contraction and subsequent activation of calcium-dependent SLO-1K channels. Recovery from the temporary paralysis is consistent with inactivation of TRP channels. Our observations elucidate mechanisms for the rapid onset and short-lasting therapeutic actions of diethylcarbamazine.